JP2012136089A - Measuring method of sidewall surface strain of tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a measuring method of sidewall surface strain of a tire, which can accurately grasp a strain state of a sidewall regardless of the size of a strain quantity.SOLUTION: This measuring method includes a silk screen plate manufacturing process, a first tape transfer process of transferring a mark to a first tape by superposing the first tape having non-expandability and stickiness on a silk screen plate, a tire transfer process of transferring the mark of the first tape to a sidewall surface by superposing the first tape on the sidewall surface along a surface shape of the sidewall of the tire before deformation, a tire deformation process, a second tape transfer process of transferring a mark of a sidewall surface to a second tape by superposing the second tape having non-expandability and stickiness on the sidewall surface along the surface shape of the sidewall of the tire after the deformation, and a strain quantity measuring process of determining the strain quantity by measuring a mark spacing after the deformation obtained by the second tape and a mark spacing before the deformation.

Description

  The present invention relates to a method for measuring a sidewall surface strain of a tire for analyzing and detecting a value of a maximum strain generated on a sidewall surface of a tire, a position where the maximum strain is generated, and the like.

  In order to manufacture a high-quality tire, it is necessary to accurately analyze and detect the value of the maximum strain generated in the tire, the position where the maximum strain is generated, and the like.

  In particular, unlike the tread portion, the sidewall portion is easily deformed, has a large amount of deformation, and has convex portions such as letters and decorations on the surface, so that cracks are likely to occur and greatly affect the durability of the tire. .

  The conventional method for measuring the sidewall surface strain of a tire is to draw a large number of parallel lines and grid meshes at equal intervals on the tire surface, and to determine the distance between the parallel lines and grid meshes when loaded and unloaded. Based on the change, the magnitude of the distortion is obtained and the position where the maximum distortion is generated is specified (for example, Patent Document 1).

JP 2003-170710 A

  However, since the data obtained from the conventional measurement method is strain data only in the direction parallel to or parallel to the parallel line, the strain state of the sidewall cannot be accurately obtained.

Therefore, a strain gauge is attached and measured, but when the deformation of the tire increases and the amount of strain is large, the gauge peels off and the resistance element is disconnected. In addition, since the gauge factor changes and a strain limit exists, it is impossible to accurately measure the amount of strain. The strain limit is generally about 20,000 to 50,000 × 10 ^{−6 in} the case of a copper-nickel foil gauge, and even in the case of a large strain gauge for a plastic region, 100,000 to 200, It is about 000 × 10 ⁻⁶ .

  In view of the above problems, an object of the present invention is to provide a method for measuring a sidewall surface strain of a tire that can accurately determine the strain state of the sidewall regardless of the amount of strain.

The method for measuring the sidewall surface strain of the tire according to claim 1 comprises:
The tire sidewall surface is measured by measuring marks on the sidewall surface of the tire by comparing the distance between the marks before and after the deformation of the tire by marking marks on the sidewall surface of the tire. A distortion measurement method,
Silk screen plate making process of providing a transfer hole corresponding to the mark on the silk screen,
A first tape transfer step of transferring the mark to the first tape by superimposing a non-stretchable and adhesive first tape on the silkscreen plate and applying a paint to the silkscreen plate;
A tire in which the transferred first tape is superposed on the sidewall surface along the shape of the sidewall of the tire before deformation, and the mark on the first tape is transferred to the sidewall surface. A transfer process;
A tire deformation step of adding a predetermined deformation condition to the tire;
A second tape having non-stretchability and adhesiveness is superposed on the sidewall surface along the surface shape of the sidewall of the tire after deformation, and the mark on the sidewall surface is marked with the second tape. A second tape transfer step for transferring to
It is characterized by comprising a deformed mark interval obtained by the second tape, and a distortion amount measuring step of obtaining a distortion amount by measuring the mark interval before deformation.

The method for measuring the sidewall surface strain of the tire of the invention according to claim 2,
The mark is transferred onto a radial line of the tire.

The method for measuring the sidewall surface strain of the tire according to claim 3 is:
The mark is transferred at regular intervals between the bead and the buttress of the tire.

The method for measuring the sidewall surface strain of the tire according to claim 4 is:
The mark is transferred at intervals in the circumferential direction of the tire.

The method for measuring the sidewall surface strain of the tire according to claim 5 is:
The mark is arranged in a rosette gauge format.

The method for measuring the sidewall surface strain of the tire according to claim 6 is:
Based on the data obtained by the strain amount measuring step, the magnitude and direction of the main strain are measured using a rosette analysis method.

The method for measuring the sidewall surface strain of the tire according to claim 7 is:
The distortion amount measuring step is a step of measuring the mark interval using a universal projector.

The method for measuring the sidewall surface strain of the tire according to claim 8 is:
The paint is composed of a mixture containing titanium oxide powder and castor oil.

  In the present invention, since the strain state is measured by measuring the change of the mark before and after deformation by providing marks freely in multiple directions at positions that are easy to analyze without using a strain gauge, The strain state can be accurately obtained.

It is process drawing which shows the measuring method of the sidewall surface distortion of the tire of embodiment which concerns on this invention. It is a figure which shows the state which has arrange | positioned the mark in the rosette gauge format in the measuring method of the sidewall surface distortion of the tire of embodiment which concerns on this invention. It is a figure which shows the state which has arrange | positioned the mark in the rosette gauge format in the measuring method of the sidewall surface distortion of the tire of embodiment which concerns on this invention. It is a figure which shows the state which has arrange | positioned the mark in the rosette gauge format in the measuring method of the sidewall surface distortion of the tire of embodiment which concerns on this invention. It is a figure which shows the state which has arrange | positioned the mark in the rosette gauge format in the measuring method of the sidewall surface distortion of the tire of embodiment which concerns on this invention. It is a figure which shows the state which has arrange | positioned the mark in the rosette gauge format in the measuring method of the sidewall surface distortion of the tire of embodiment which concerns on this invention. It is a figure which shows the state which has arrange | positioned the mark in the rosette gauge format in the measuring method of the sidewall surface distortion of the tire of embodiment which concerns on this invention. It is a figure which shows typically the 1st tape transcription | transfer process in the measuring method of the sidewall surface distortion of the tire of embodiment which concerns on this invention, Comprising: (a) is sectional drawing, (b) is a top view of a 1st tape. It is. It is a figure which shows the transcription | transfer position of the mark on the sidewall surface in the measuring method of the sidewall surface distortion of the tire of embodiment which concerns on this invention. It is a figure which shows the measurement result of the distortion of an Example. It is a figure which shows the magnitude | size and direction of distortion by the arrow of an Example. (A) is a figure which shows the change of the distortion amount of an Example, (b) is sectional drawing which shows the bending shape of the tire at the time of a deformation | transformation of an Example.

  Hereinafter, the present invention will be described based on embodiments.

  As shown in the process diagram of FIG. 1, the method for measuring the sidewall surface strain of the tire according to the present embodiment includes a silk screen plate production process S1, a preparation process S2, a first tape transfer process S3, a tire transfer process S4, and a tire. A deformation step S5, a second tape transfer step S6, and a strain amount measurement step S7 are provided. Hereinafter, each step will be described.

(1) Silk screen plate production process A silk screen plate is produced by attaching a paint shielding film to a silk screen stretched on a frame. It is preferable that the shape and position of the transfer hole provided in the paint shielding film correspond to the shape and position of the mark arranged in the following rosette gauge format.

  Here, the arrangement of marks in the rosette gauge format will be described.

  FIG. 2 is a diagram showing a state in which marks are arranged in a rosette gauge format in the measurement method of the present embodiment. 3-7 is a figure which shows the state which has arrange | positioned the mark in the rosette gauge form of another aspect (Hereinafter, FIGS. 2-7 which have arrange | positioned the mark are called marking).

  In FIG. 2, the marks are arranged so that the three imaginary line segments indicating the mark intervals form a “three-axis 45 ° intersecting type” that intersects at 45 °.

  In FIG. 2, a dotted line indicated by 10 is a virtual line segment identified by + marks indicated by 11 and 12 at both ends, and a dotted line indicated by 20 is identified by + marks indicated by 21 and 22 at both ends. A dotted line indicated by 30 is a virtual line segment identified by + marks indicated by 31 and 32 at both ends. G is a point where a main distortion or the like is required, and is located at the intersection of three virtual line segments 10, 20, and 30, and indicates an average distortion between markings.

  Other three-axis types include a “three-axis 45 ° convergence type” (FIG. 3) and a “triaxial 60 ° triaxial type” (FIG. 4), and a four-axis type includes “ There are “intersection type” (FIG. 5), “convergence type” (FIG. 6), and “T delta type” (FIG. 7), which are appropriately selected according to required accuracy. In the figure, 40 indicates a fourth virtual line segment 41 and 42 indicate marks at both ends of the virtual line segment.

(2) Preparatory process A titanium oxide powder and castor oil are mixed, and if necessary, a plasticizer such as DOP is added to prepare a marking paint to be applied to a tire. Further, after determining the measurement cross section (position) of the tire and performing the surface treatment of the tire, the tire is attached to the testing machine.

(3) First Tape Transfer Process FIG. 8 is a diagram schematically showing a first tape transfer process in the method for measuring a sidewall surface strain of a tire according to the present embodiment, where (a) is a cross-sectional view. (B) is a top view of a 1st tape. As shown in FIG. 8, a plurality of markings are applied to the first tape T1 by superimposing the first tape T1 on the silk screen plate 2 and extruding the paint 4 with the squeegee 3 to apply the paint 4 to the silk screen plate 2. Transcript. FIG. 8 shows an example of nine markings. A reference tape is prepared in advance in the same process as the first tape transfer process for subsequent strain measurement. In the figure, T11 is a base material of the first tape, and T12 is an adhesive. Further, (a) of FIG. 8 shows a cross section of a portion corresponding to the portion surrounded by the rectangular frame of (b).

  The first tape T1 is preferably a non-stretchable tape such as a mending tape (registered trademark) that can be peeled off after adhesion. The same applies to the following second tape and reference tape.

(4) Tire transfer step For the untransformed tire, the length direction of the first tape is aligned with the radial direction of the tire, and is, for example, along the tire ground contact center line. Then, the first tape is superposed on the sidewall surface and adhered to the sidewall surface so as to follow the surface shape of the sidewall. Next, after rubbing from the top of the first tape, it is peeled off. Thereby, a plurality of markings on the first tape are transferred to the tire surface.

(5) Tire deformation step The tire is deformed according to predetermined conditions. Tire deformation is measured when the inflation is measured with the deflated time as the reference, when the strain when the load is measured with the inflation time as the reference, and when the inflation (small internal pressure) is used as the reference. There are various cases, such as when measuring the strain at a large value of internal pressure).

(6) Second Tape Transfer Process Next, the second tape is superimposed on the sidewall in accordance with the surface shape of the deformed tire sidewall, and a plurality of markings on the deformed sidewall surface are secondly applied. Transfer to tape.

(7) Strain amount measurement step Next, each strain amount is obtained using a universal projector in the following manner, and the magnitude and direction of the main strain are obtained based on the rosette analysis method.

(A) Measurement with a universal projector and calculation of the amount of distortion, etc. The second tape from which the marking after deformation is acquired and the reference tape from which the marking before deformation is acquired are installed on the stage of the universal projector. Affix to the acrylic plate.

  The universal projector projects the optical image of the object to be inspected (a mark on the second tape and the reference tape) on the stage (acrylic plate) onto the screen at an accurate magnification, and measures the length based on the projected image. By dividing the length by the nominal magnification of the objective lens, an accurate measurement value can be obtained.

  Then, for each of the three virtual line segments in the three-axis 45 ° intersection type, the change in the distance between the marks on both ends is obtained, the expansion and contraction of the tire along the virtual line is obtained, and the expansion and contraction amount of each virtual line is calculated Divide by the distance between the marks on both ends to find the amount of distortion.

(B) Analysis based on rosette analysis method Based on the rosette analysis method, the center position of the line segment from the change in length (strain generated in the tire) and the direction of the line segment shown in FIG. The values of the maximum principal strain (εmax), the minimum principal strain (εmin), the maximum shear strain (γmax) and the direction of the principal strain are obtained. In addition, the maximum principal stress (σmax), the minimum principal stress (σmin), and the maximum shear stress (τmax) are obtained from the elastic modulus, Young's modulus, and Poisson's ratio of the tire material at the location.

(8) Measurement of surface strain distribution FIG. 9 is a diagram in which markings are transferred at equal intervals in the circumferential direction of a tire, 50 is a tire, 51 is a grounding center line, 52 to 57 is a center line, 60 is a table, F is a load acting on O, and an arrow indicates the direction of the load F.

  As shown in FIG. 9, the surface strain distribution can be measured by transferring the marking transfer position at intervals in the circumferential direction of the tire, not limited to the tire ground contact center line 51 as described above. .

  As described above, when the marking is also arranged in the circumferential direction of the tire, the measurement is performed by transferring a plurality of tapes to respective center lines in FIG.

(Effect of this embodiment)
The measurement method of the present embodiment described above has the following effects.

(1) Since the first tape on which the marking is transferred is superposed on the sidewall surface along the surface shape of the sidewall of the tire before deformation, the marking is transferred onto the sidewall surface. Unlike lines and grid meshes, the markings can be freely placed in multi-directional positions that are easy to analyze.

  And, since the marking on the side wall surface is transferred to the second tape so as to overlap the side wall surface shape of the tire after deformation, the strain data after deformation can be obtained accurately. it can. In addition, unlike the case where a strain gauge is attached, it is possible to follow large tire deformations and to acquire strain data of large deformations.

  As a result, the distortion state of the sidewall can be accurately obtained regardless of the magnitude of the strain amount in the strain amount measuring step for obtaining the strain amount by measuring the post-deformation mark interval and the pre-deformation mark interval.

(2) Since a silk screen plate is used for transfer, there is no disorder in the position and shape of the marking, and more accurate strain data can be acquired.

(3) Since the marking is transferred onto the radial line of the tire and is transferred at regular intervals between the bead and the buttress, main strain data in the radial direction of the tire can be acquired. Further, since the marking is transferred at intervals in the circumferential direction of the tire, the strain state of the entire tire sidewall surface can be obtained.

(4) Since the magnitude and direction of the main strain are obtained using the rosette analysis method, the magnitude and direction of the main strain can be easily and accurately obtained using a known calculation method.

(5) Since the mark interval is measured using a universal projector, accurate distortion data can be easily obtained.

(6) The paint uses a mixture containing titanium oxide powder and castor oil. Since the titanium oxide powder is white, the position of the mark becomes clear, and both the titanium oxide powder and castor oil are used for the silk screen plate. Even maintenance is easy.

  In this example, using tires A to E having different specifications, a surface strain measurement test is performed based on the above-described embodiment, and a durability test is separately performed. The relationship between the strain and the crack index obtained in the durability test is considered (Examples 1 to 7). For comparison, tires A and B were also measured by a conventional strain gauge method (Comparative Examples 1 and 2).

(Test tire)
In each example and comparative example, five types of tires having different ply materials and ply winding heights were used.
Size: 215 / 45R17

A. Surface strain measurement test The surface strain measurement tests of Examples 1 to 7 were performed according to the following steps.

1. Silk Screen Plate Making Process A silk screen plate having a marking width shown in Table 1 was produced in a triaxial 45 ° crossing type. The silk screen version is used repeatedly.

2. Preparation Step (1) Production of Marking Paint First, a marking paint was produced. Specifically, 10 to 20 g of plasticizer (DOP) was added to 100 g of titanium oxide, and then kneaded while adding 30 to 40 g of castor oil little by little to prepare a marking paint.

(2) Determination of measurement cross section (position) For the sidewall part, the inner liner joint and ply joint positions were removed, a place with as little as possible unevenness was selected, and two measurement points on the circumference were marked with chalk.

(3) Attaching the tire to the testing machine After attaching the tire to the testing machine, the tire was inflated and adjusted to a predetermined internal pressure (220 KPa).

3. First Tape Transfer Step (1) Attaching Mending Tape A mending tape (manufactured by Sumitomo 3M) was affixed to the mark position on the front side of the silk screen.

(2) Application of paint The paint was applied in the same direction using a squeegee from the back side of the silk screen. Thereby, the mark of the paint was formed in the predetermined position of the mending tape. Thereafter, the mending tape was peeled off from the silk screen. Two mending tapes were basically prepared, one for reference and the other for measurement.

4). Tire transfer process A mending tape for measurement was applied to the measurement cross section (position) and rubbed to transfer the mark from the mending tape to the tire sidewall.

5. Tire deformation process The measurement cross section (position) was set at the center of contact and a longitudinal load of 6.1 kN was applied.

6). Second Tape Transfer Process The marking at the time of loading was transferred to a new second mending tape and then pasted on a transparent sheet.

7). Strain amount measuring step The reference mending tape and the transparent sheet on which the second mending tape obtained above was affixed were set on a universal projector, and the state of expansion and contraction in each marking was measured. And the strain state was calculated using the calculation method of Rosetta analysis.

B. Endurance test The tires of each example and comparative example were mounted on a standard rim, the inner pressure was 220 KPa, the load was 1.15 times the maximum load capacity, and the tire side was irradiated with ozone at a speed of 80 km / h. After traveling 15,000 km, the size, depth, and number of cracks on the tire side were measured, and evaluation was performed with an index (crack index) where the measurement result in a B-spec tire was 100. The smaller the crack index, the better the durability.

C. Measurement Results Table 1 shows the measurement results in the surface strain measurement test and the durability test.

  As shown in Table 1, even in the tires of the same specifications (Example 2 and Comparative Example 1, and Example 5 and Comparative Example 2), in Examples 2 and 5 measured by the marking method, the maximum The main distortion is measured. On the other hand, in Comparative Examples 1 and 2 using the conventional strain gauge method, measurement was not possible because the strain gauge failed to follow the occurrence of strain and was damaged.

  Further, from Table 1, it was confirmed that there is a certain correlation between the maximum principal strain and the crack index, as already known. That is, it was confirmed that correct measurement was performed by the measurement method of the present embodiment. Thereby, durability can be predicted by measuring the maximum principal strain using the above measurement method.

  FIG. 10 is a diagram showing the measurement results of the strains of Examples 3, 6, and 7. In FIG. FIG. 10 shows measurement results when the marking width and the number of markings are changed using a D-spec tire. FIG. 10 shows that the measurement result changes depending on the marking width (the interval between the marks). In particular, in the case of Example 7 with a marking width of 10 mm, it is 14%, which is significantly lower than 17% and 18% of other Examples 3 and 6.

  FIG. 11 is a diagram showing the tire measurement position, strain magnitude and direction of Example 3, and FIG. 12 is a diagram showing changes in strain amount of Example 3 (a) and a modification of Example 3. Sectional drawing (b) which shows the bending shape of the tire at the time is shown. 11 and 12, the maximum tire width position of the portion that is most bent at the center of the load is extended in the tire radial direction (90 degrees), and accurate measurement can be performed by using the measurement method of the present invention. I understand.

DESCRIPTION OF SYMBOLS 1 Silk screen 2 Silk screen plate 3 Squeegee 4 Paint 10, 11, 12 Virtual line segment and its markings 20, 21, 22 Virtual line segment and its markings 30, 31, 32 Virtual line segment and its Marks 40, 41, 42 at both ends Virtual line segments and marks 50 at both ends Tire 51 Grounding center lines 52-57 Center line 60 Stand T1 First tape T11 Base material T12 Adhesive

Claims (8)

The tire sidewall surface is measured by measuring marks on the sidewall surface of the tire by comparing the distance between the marks before and after the deformation of the tire by marking marks on the sidewall surface of the tire. A distortion measurement method,
Silk screen plate making process of providing a transfer hole corresponding to the mark on the silk screen,
A first tape transfer step of transferring the mark to the first tape by superimposing a non-stretchable and adhesive first tape on the silkscreen plate and applying a paint to the silkscreen plate;
A tire in which the transferred first tape is superposed on the sidewall surface along the shape of the sidewall of the tire before deformation, and the mark on the first tape is transferred to the sidewall surface. A transfer process;
A tire deformation step of adding a predetermined deformation condition to the tire;
A second tape having non-stretchability and adhesiveness is superposed on the sidewall surface along the surface shape of the sidewall of the tire after deformation, and the mark on the sidewall surface is marked with the second tape. A second tape transfer step for transferring to
Measuring the sidewall surface strain of a tire, comprising: a mark interval after deformation obtained by the second tape; and a strain amount measuring step for obtaining a strain amount by measuring the mark interval before deformation. Method.   2. The method for measuring a sidewall surface strain of a tire according to claim 1, wherein the mark is transferred onto a radial line of the tire.   3. The tire sidewall surface strain measuring method according to claim 1, wherein the marks are transferred at regular intervals between the bead and the buttress of the tire.   4. The tire sidewall surface strain measurement method according to claim 1, wherein the mark is transferred at intervals in the circumferential direction of the tire.   The method for measuring the sidewall surface strain of a tire according to any one of claims 1 to 4, wherein the mark is arranged in a rosette gauge format.   The tire according to any one of claims 1 to 5, wherein the magnitude and direction of the main strain are measured using a rosette analysis method based on the data obtained by the strain amount measuring step. Method for measuring side wall surface distortion.   The said distortion amount measurement process is a process of measuring the said mark | interval space | interval using a universal projector, The sidewall surface distortion of the tire of any one of Claim 1 thru | or 6 characterized by the above-mentioned. Measuring method.   The method for measuring a sidewall surface strain of a tire according to any one of claims 1 to 7, wherein the paint is made of a mixture containing titanium oxide powder and castor oil.

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